java折半查找（正常的折半查找）

import java.util.Scanner;

/**
 * @author Administrator 折半查找
 */
public class zhebansousuo {

    public static void main(String[] args) {
        int[] a = new int[100];
        int x, b;
        Scanner cin = new Scanner(System.in);
        x = cin.nextInt();

        for (int i = 0; i < x; i++) {
            a[i] = cin.nextInt();
        }
        b = cin.nextInt();
        System.out.println(sea(a, b, 0, x));

    }

    public static int sea(int[] a, int x, int beg, int last) {
        int mid;
        if (beg > last) {
            return -1;
        }
        while (beg <= last) {
            mid = (beg + last) / 2;
            if (x == a[mid]) {
                return mid;
            } else if (a[mid] < x) {
                beg = mid + 1;
            } else if (a[mid] > x) {
                last = mid - 1;
            }
        }
        return -1;
    }

}